Petroglyphs in the desert

People used to live in the Painted Desert.  They've left behind some marks of their presence.
Petroglyphs.

These are some of the best preserved petroglyphs in the U.S.  They're around 1000 years old, so most of their meanings are lost.
Maybe they were solar calendar markings.
Maybe they were messages to other migrating tribes.
Maybe they commemorated important events.

Maybe one day we'll figure it out.